text:
If I'm cleared for the approach while established in a hold, can I turn inbound immediately?
If you are established in holding and on an outbound leg (say you are 30 sec outbound on a 1 min or 3.5nm on a 7nm leg) and you are subsequently “cleared approach,” are you allowed to immediately turn inbound to commence the approach or are you required to continue fly outbound according to the published pattern? Is there an FAA reference?
Note: not HILOPT

Welcome to aviation.SE! This seems very similar to this question; does it help?

I think this question is different. As I read them, this q asks whether you can truncate a hold when given an approach clearance, the other q asks if one extra "lap" is required after clearance.

Functionally identical questions though, and with the same answer:  When cleared for an approach you are expected to commence the approach with no undue delay.

Yes, unless ATC instructions/charted instructions specify something to the contrary, you can immediately turn inbound for the holding fix, as long as you stay within the protected area till you leave the holding fix for the approach.


text:
Symbol found on an IFR low chart
I see this symbol on an IFR low chart, can someone tell me what it is?

Does the symbol have an associated name depicted? Or if you right-click the area on Skyvector, can you see the name? Look that name up in the FAA's 8260-2 database and it should tell you all you need to know.

This symbol appears, e.g. on enroute charts. What puzzles me is you were not able to find it on the chart legend.

More context would be better. The screenshot you posted indicates that there is a navaid information box above and to the left of the symbol, but you cut it off so we cannot see what it says. If we knew the name of the navaid we could search for it in the 8260-2 database and we would know more about it.
But just the symbol itself is enough to know exactly what it represents (which is the point of there being a symbol at all, of course). As TomMcW pointed out, everything you need to know about the charts can be found in the Chart User's Guide. However, it is not a Compass Locator Beacon but rather a Non-Directional Beacon. (A compass locator is a specific use case of an NDB.)
We can see the difference in the two symbols when they are side-by-side:

Left: CLB; Right: NDB

A Compass Locator Beacon has two layers of larger and darker brown dots surrounding its central circle, while a normal NDB has four layers of smaller and lighter brown dots. The image you posted clearly depicts an NDB and not a CLB.
You will find CLBs associated with instrument landing systems, as Tom said. NDBs may also be depicted as the outer marker of an ILS, but they can also appear elsewhere, for example on an airport proper.

On the US low enroute charts, NDB and locator have the same appearance. However in the OP there is a North arrow, which seems to indicate a NDB. Why is there a North arrow is another question...

@mins I'm not sure that's correct. Look at L-27 and compare ACORE (CP) with ALGOA (JE). They are different symbols. (Note that both symbols include North arrows, as do on-airport NAVAIDs like Bloomfield [BEX].)

You're right, so the legend is wrong?? CP symbol doesn't seem to be part of the legend.

@757toga: Good information. So we have the NDB, regular large symbol, then the compass locator (low power but same symbol), then the locator collocated with the a marker/LOM/LMM, (smaller symbol). Do you know when North arrows are used?

Even more confusion if we add Jeppesen to the loop. Only three rings. The best is to accelerate NDB and locators decommissioning!

@mins, being a low en-route chart the marker function should not be relevant, so I would expect the number of dots, if it varies on a given chart, to indicate the power/range, no? A low power NDB makes little sense outside an approach, so the fewer dots would only be seen as LOM/LMM, but a high power NDB can still be a LOM (e.g. when it is the only navaid in larger area).

@JanHudec: That seems logical, and would match the smaller size of the locator on FAA charts. Still this symbol on enroute charts is a mystery.

The reason I thought it was a compass locator is the north arrow. I've never seen an ndb with an arrow but not a full compass rose.

@mins I understand that symbol as NDB (there is frequency 350 given for it), which happens to be co-located with a marker beacon, but that is not really relevant for en-route navigation. It might be smaller because of graphical considerations even. I am somewhat surprised they bothered with the ILS at all (it does not have all or even most ILS).

@JanHudec: After searching a bit on compass locator, I have clarified a locator is just a certain category of NDB (class L, 15NM range, other classes are MH, H, HH), used specifically for collocation with an ILS marker. As a NDB is has an individual frequency and identification morse code associated. There name comes from ADF predecessor: radio compass.

It is a compass locator beacon1. It’s an NDB located at the outer marker of an ILS. Despite the name it has nothing to do with a compass. According to ARGOTI it is called that because the name “actually comes from the old radio compasses installed on airplanes.”
1 From FAA Aeronautical Chart User’s Guide pg. 70.

Why do you think it’s a locator rather than an NDB?

It is not a compass locator beacon. Compass locator beacons have a two-layer circle of brown dots around the central circle; OP's icon has a four-layer circle of brown dots, indicating that is an NDB.

@zachinquarantine Please accept the other answer. I have misidentified the symbol.

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Is it possible to take off backwards using reverse thrust?
Last night I had a wild dream where an airliner took off into the air backwards from the departure gate. I'd like to know just how impossible this is. Let's ignore the perils of starting a takeoff roll from the apron.
Is there any fixed-wing aircraft in which it's possible to use full-power reverse thrust to achieve backward flight? Either:

To gain altitude using forward flight and then transition to backward flight, or
To take off from a runway of any length?

I know that aircraft equipped with reverse-thrust have interlocks to prevent engaging the reversers in the air. Assume these interlocks are somehow defeated.

I think you might want to ask whether backwards flight is actually possible at all.

I doubt a Boeing 747 would takeoff that way, even if it accelerated to Mach 10 …

Welcome to aviation.SE! This question and this one might help to answer your question.

Notice that nobody is even bothering to address the "transition from forward to reverse flight" part of the question?

Did you mean "controllable" flight?  If not, just about anything is arguably possible

If you can do it with a model aircraft, then you can theoretically do it, which would then make taking off backwards "possible". I'm pretty sure some model aircraft somewhere can do that. Also, it appears to be possible to fly backwards to some extent with real-sized aircraft. I'm no expert so I won't try to answer this. But here's a link: https://www.bbc.com/future/article/20150415-the-plane-that-can-fly-backwards

Actually that would be a pretty cool project. Build a radio-controlled model airplane that can take off in either direction.  Reverse thrust is now widely available with electric motors.  Surely it would be possible-- you might need a canard stabilizer as well as a conventional stabilizer, and each might need to move to a different position (incidence) for forward versus backwards flight--

Re vertical fins, have one in front and one in back, whichever one is "leading" could go to a free-swivelling mode so as to effectively remove it's influence from the stability dynamics (or is that cheating?)  --

Back to the horizontal surfaces, instead of canard plus conventional, you could have a single set of all-moving surfaces, that is conventional when the plane is going forwards and canard when the plane is going backwards, combined with a heavy weight (e.g. the battery) that shifts forward or aft to move the CG depending on the direction of flight--

Four reasons among many others it's not possible:

Weathervaning effect from the vertical surfaces of the tail would turn the aircraft as it accelerates, the tail would not remain upstream of the nose.

Taking off requires the engines to deliver their maximum power and the wing to convert this power into lift very efficiently to leave the ground. The poor efficiency of a reversed wing prevents generating required lift.

Thrust available from reversers is significantly weaker than regular thrust.

Takeoff rotation would be done with the nosewheel bearing all aircraft weight. Being not designed for this load, it would collapse.

Weathervaning effect
Perhaps the most simple to understand difficulty is the aircraft tendency to weathervane, to behave like a weathercock when airspeed is significant.
As the vertical surfaces of the empennage are large, having them upstream of the engines makes the aircraft instable in yaw. As soon as the aerodynamic force is significant, the tail is slowed down, and this tendency, unless taken into account in the design, cannot be stopped before the tail is the rearmost flying part.
The more a multi-engine aircraft is powerful, the larger is the vertical empennage, in order to be able to maintain the desired yaw in case an engine is inoperative.
A wing is not reversible
Engines are designed to deliver their maximum thrust when an aircraft takes off (TOGA -takeoff / go around- setting). This maximal thrust must be efficiently used by the wing, which is required to have a given lift capability at this time. This is the case when the aircraft is accelerated in the regular direction.
(I would tend to say a wing cannot work at all in the reverse direction. It is fitted with asymmetric moving surfaces, likely to disintegrate when not loaded as intended, hinges being now at the wrong place. This is also valid for the tail surfaces. But let's assume everything remains in one piece.)
When airfoil edges are swapped, a condition known as reverse flow. Lift cannot be generated except at small angles of attack. This condition can happen on helicopter rotor blades and is classical for tidal turbines though the applicable Reynolds number is different.
The problem is the airflow does not attach well to the upper surface when the leading edge is sharp, stall occurs at small angles of attack. By itself the stall problem is a no go for taking off, as takeoff require a high angle of attack (15°).
If we want want to ignore this, we face a second problem: Reverse flow also introduces a dramatic loss of efficiency (L/D ratio). Lift is at least divided by two, and drag multiplied by two. This too is a condition preventing taking off. (Note the factor would probably be more like 10, but I've no reference to support this figure. More on that aspect. By the way this could make a good question and we have aerodynamics experts able to answer.)
To compensate lift loss takeoff speed needs to be increased, this requires more thrust and a longer runway to accelerate. Compensating for higher drag requires more thrust too.
At this stage, even with we had the full regular thrust, this wouldn't be enough to make the aircraft airborne. Instead of two engines we would need four or more.
Reverse thrust is limited
Engines provide reverse thrust at the expense of significant losses. Reversers design is very ineffective in term of aerodynamics as airflow is strongly deflected.
In addition only a fraction of thrust is reversed and some direct thrust is still generated. We can estimate the effective reverse thrust to be only 70% of TOGA.
While more than normal thrust would be needed, the thrust actually available is reduced and totally insufficient to take off.
When the engine is used in forward direction, air enters the engine pushed by ram pressure. When used in reverse direction, ram pressure is actually negative, air is constantly moved away from the inlet, the engine is not fed correctly, the compressor likely stalls and stops functioning before reaching the takeoff speed.
In a turbofan, the reverser reverses the fan flow, but the regular core flow is still required to spin the engine. It leaves the engine at the exhaust, which is now subject to ram pressure. The turbine is not designed to work in these conditions.
Aircraft attitude to take off
Now the visual part. In a regular takeoff, at the end of the acceleration roll aircraft nose is raised to increase the angle of attack (rotation phase), so the wing can generate the amount of lift required to leave the ground. When the aircraft is used in reverse gear, this gives this:

Aircraft image source, adapted
Assuming elevators are effective to lift the tail, which is not granted, there is an impossibility to balance the aircraft on the nosewheel during the roll and to keep it on the centerline, which is anyway not visible by the pilot.
The regular rotation is eased by the main gears location and the main gears are able to bear all the weight until the aircraft is airborne. In your dream the weight is now fully on the nose wheel, and the nosewheel is unable to resist, it collapses.

There are other points, which would be boring to explain but which are as significant, e.g. how to aerodynamically control the aircraft during the takeoff and in flight, as control surfaces wouldn't be movable under the reversed ram pressure.

Re "A wing is not reversible" -- in the case of a rudder-elevator-throttle (no ailerons) radio-controlled model airplane, I've seen a photo of the rubber-band-on wing installed backwards (trailing edge first).  Word is it was flyable and controllable, with some loss in performance.  (As I recall, very abrupt stall characteristics were reported.)  Airfoil was probably flat-bottomed and probably somewhat along the lines of the classic "Clark Y".  Will look for links.

@quietflyer what is the wing loading of the model, though? A fair bit lower, probably low enough it didn't need an airfoil.

You're obviously right but while An engine delivers its maximum power for takeoff, there is practically no way to get more from it. there is a way to need less power from it - take off empty with minimum fuel

You actually created an image to illustrate this? Impressive! Here, take my upvote!

@ChrisH: This is right of course, and other optimizations in mass and balance could be done too if the reverse takeoff had to be tested. On the other hand assuming the lift is only half in reverse direction is way optimistic. The aircraft will never by light enough.

@mins of course.  The only way you'd get a jet to fly backwards (negative airspeed) is thrust vectoring as on the Harrier, though most of the thrust is supporting the weight at that point.  Something with a low enough stall speed (the Belphegor) should be able to get negative ground speed for an apparent backwards movement as is relatively common on light propeller aircraft.

One more factor could be added, related to the first one: The center of gravity will be too far behind in backwards flight, so the airplane will be extremely unstable.

Now what about if you had a very strong headwind?  Ignoring that this is basically unheard-of, let's say there was a 300mph wind blowing directly down the runway towards the plane.  If the plane took off the normal way (not with reverse thrusters), it could gain lift while appearing to move backwards relative to the ground...

Regarding the landing gear part... this is very true for a normal tricycle gear aircraft, but wouldn't really hold for a taildragger or something like a B-52, would it?

@reirab: Some particular aircraft may not fail on the last of the four points listed, yes. This could be explained in alternate answers.

It seems to me that the empennage must be behind the center of mass, not necessarily behind the engines. The aircraft will pitch and yaw around the center of mass.

Sadly all of the points here are false. The weathervaning is controllable with rapid accurate rudder and elevator input. wings are reversible, just horridly inefficient. Reverse thrust is weaker, but what is the baseline, if base engine is 3X stronger than needed, 30% of that is enough!, and who says you need apply any pressure on the ground wheels when rotating, there is nothing inherent in aerodynamics that requires this. None of the listed issues are a showstopper, they all just make the process more difficult and awkward, not inherently impossible.it is impossible, but wrong reasons

@PcMan: What you say would be possible only with a specifically designed aircraft, with triple power, larger wing, high g rudder, etc. That aircraft itself won't exist in the real world. The question is about an existing aircraft, so your comment is irrelevant except the two last words "wrong reasons", and your downvote is gratuitous. What would be interesting, is to know the "actual reasons". Can you be constructive now and post a full answer to share your experience?

a wild dream (the Langoliers chewed up the runway ahead) so...

Theoretically, if you got the passengers to move rearward a bit and retracted the nosewheel to rotate, given the plane was somehow light enough and generating enough thrust, the resultant aircraft would be the latest in canard design with forward swept wings.  With the right CG placement, possible, but ...

the ailerons, flaps, rudder, and stabilator are not designed to be reverse flown in 150-250 knot winds and would likely fail when deflected, as well as the wingtips.

Even if it got off the ground, a crash would likely rapidly ensue.

Theoretically, yaw instability from forward vertical fin would make it nearly impossible.  Stability on roll and pitch axes would be sufficient for a good movie plot.  Essentially it would be a Pterodactyl in need of a computer for yaw control.

good use of the word "nearly".

Simple answer is no.
At current technology reverse thrust is not strong enough to push aircraft back even to take off speed. Use of thrust reversal at low speed can be harmful to the engine itself due to high risk of foreign object damage. Lastly wings are not design to efficiently generate lift in backward direction so you need more airspeed hence more thrust to have enough lift for flight.
If you go so far as to redesign the plane to efficiently fly backward the result would look very similar to a normal plane. You will not have anything new.

Possible damage to the engines is not just from FOD. We once had a mystery problem where splines joining two parts of the main engine rotor were wearing out much faster for one airline than any others using the same engine/airframe combination. It turned out that their pilots were routinely using maximum reverse thrust to push back on the apron for departure, instead of waiting for a tug.

I guess the next assignment is to design a "reversible" plane that can fly equally well either forwards or backwards.  Step one is to put the engines on motorized swivel-mounts...

@JeremyFriesner: I think a push-pull prop design would be simpler and work better.  A bigger issue would be the center of gravity, but perhaps that could be dealt with by having cargo holds at both ends of the plane, with a requirement that whichever end would be in front have more cargo than the other end (using ballast if there wasn't enough useful cargo to be transported).

Another concern with low forward speed use of reverse thrust is the engine ingesting the air blown out from the reversers. This is a concern at low forward speeds, but it's even more of a concern at all reverse speeds. There's a good chance that you'll have a compressor stall on your hands before you ever got to the point of rotation.

Since it's only airspeed that matters, if you give up on the reverse thrust bit, you just need a strong enough wind blowing parallel to the runway.
So if you're taking off into a category 5 storm with 140 knot winds, you could be traveling down the runway backwards pretty fast in a small plane. And you'd climb out of the airport still going backwards in ground speed terms.
On a smaller scale, think of wind tunnels. Airspeed is what matters, so a stationary model can fly given sufficiently strong wind.
(Ignoring all the ways the storm would destroy your plane and kill you, of course).

You can do the same with a kite in low wind. But this is still a forward flight. The question is about backward flight not about negative or null ground speed.

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text:
Is it common for panels on a plane's body to not be perfectly aligned?
I was recently on a RyanAir flight. As far as I know, they use Boeing 737.
When boarding, I noticed a that one of the panels' edge, roughly where the head / chest part of the logo is, was sticking out maybe 4-5 mm compared to the edges of the neighboring panels.
This wasn't something new because the paint above was in perfect shape.
Is it common for panels on a plane's body to not be perfectly aligned like this? I never noticed this on any other plane I boarded.

The best illustration I could find is a bathroom tile picture:

The skin on the right of the door looked exactly this: one panel had one side not flush with the others and intact paint on top of the whole thing.

You need to provide a bit more detail, like a diagram or sketch.  It sounds like you were noticing a skin lap joint (ie, not flush, with a step of perhaps .063" from one panel to the other).  Lengthwise skin joints are sometimes done that way because it's a lot simpler and there is minimal drag penalty. Or it's some kind of reinforcing doubler plate or patch that steps down to adjacent skin.

I‘ve seen brand new aircraft with joints across the flow direction (i.e. barrel to barrel) with steps of a couple of millimeters between some panels.

Yeah once you are away from the nose, the turbulent boundary layer is deep enough that lap seams don't have a major drag impact.  However you will almost always see a sealant fillet to make the joint kind of wedge shaped instead of straight step.

I added a picture to better illustrate

@JohnK No, 4-5mm is about 0.16-0.2in, which is about 3x bigger than you suggest. (Also, it's kinda silly to say "perhaps" and then give a measurement to the nearest thousandth of an inch, as if people can eyeball measurements to about the precision of the thickness of a piece of copier paper.)

Yeah when I wrote it it was in the back of my mind that people would be puzzled by such a precise number.  I used .063 because that's a typical standard skin thickness for Alclad sheet you'd expect to see on an airliner of that size.  I assumed @Thomas was making a wild guess on what he was seeing while filing past the door, and probably overestimating.

yes, I definitely estimated it from a distance, so it could be quite off

It looks like you were seeing simple skin lap joints.  Flush skin butt joints are generally used on high speed aircraft, but these joints are more complex to make (you have to use a joining splice strip under the butt joint).
A lot of the time the manufacturer determines that the local airflow isn't smooth right at the surface (there is a turbulent boundary layer that is maybe 1/8" deep) and a small step in the surface has a negligible effect on drag.  If this is the case, a simple lap joint, that doesn't require the joining splice strip underneath, is used.
There usually isn't a hard 90 degree step on lap joints because it's normal practice to put a fillet of sealant along the edge to make the higher skin taper toward the lower one and this mitigates any drag effects further.

Yes, different manufactures have different tolerances. When I worked for Continental Airlines ~1998-2004 as a ramp supervisor, I often commented on the difference between Aerobus and Boeing. I preferred to work on Boeing aircraft but Aerobus aircraft were much smoother and prettier.
A good example is the flap track covers. Boeing flap tracks have large gaps and generally sharper corners, while Aerobus has very little if any gaps and smooth fillets. Boeing engine cowls where sometimes so mismatched that it would take two or three of us pushing and twisting to get the latches locked - Aerobus cowlings are a work of art!
Most of my work was on Boeing-757 and you could tell Boeing had started to take closer attention to detail - for example the gears doors and wing/fuselage streamlining was much neater than previous Boeing aircraft. Boeing-737 are very crudely made. It did seem like Boeing was improving the quality on the 777 and even more on the 787. FYI - McDonnell Douglas probably had the worst gaps, seals, and panel mismatch I observed.

Aerobus 380 flap track

Aerobus? Do you mean Airbus?


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What windshield washer fluids do aircraft use?
What are the fluids currently used on commercial aircraft that have an in-flight windshield washer system (not just a wiper)?
And if they exist, are there fluids more "ecological" that could have a good cleaning capacity, especially on salt?

How would you get salt on the windshield?

@RonBeyer around the world there are airfields next to the sea. wind will carry the salt on the windshield for you.

There are, or were, alcohol based windshield anti-ice systems that sprayed it like a car.  The Twin Otter had one, but the system was removed after an alcohol fueled cockpit fire that burned the pilot pretty bad back in the late 70s.

Some aircraft do have windshield washers as part of the windshield wiper system. The washer fluid used is usually some combination of isopropyl alcohol, methyl alcohol, ethylene glycol, or propylene glycol.
Two brand names are TKS and Kilfrost.
TKS is 85% Ethanediol(ethylene glycol), 5% Isopropanol(isopropyl alcohol), and 10% Distilled water.
Kilfrost is also ethylene glycol, isopropyl alcohol, and pure water
In the past some aircraft also used these same fluids for windshield anti-ice/de-ice systems.
I am not aware of any “ecological” substitutes.


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How is bleed air flow related to thrust level?
I read that the bleed flow negatively affects the thrust levels for a turbofan engine. However, I was wondering if vice-versa is true as well? Whenever the thrust levels for a turbofan are lowered at the same conditions, does the bleed flow value also decrease? What practically happens in an engine?

It looks to be more of an on-demand supply than a fixed portion of the engine airflow, otherwise the passengers would not be ccomfortable during approacha md landing. Some quantifications in this answer and this one

Okay, so what I understand from this is that bleed flow (customer bleed) is dependent on the requirement and not a fixed value, and may change depending on the aircraft/engine operating thrust or power level (e.g. during LTO cycle). Have I got it right?

When they say it negatively affects thrust they mean that taking bleed air results in less thrust being generated just like running the AC in your car “robs” the engine of power that could otherwise be delivered to the wheels.

Related

Bleed air pressure is not directly linked to the passenger cabin.
Bleed air is used to power air cycle machines which provide cabin pressurization and temperature control. The bleed air supply is regulated so that a minimum constant supply is maintained over a wide variety of engine operating parameters.
Bleed air is also often used in other aircraft systems. Wing anti-ice, engine anti-ice, and engine starting are 3 more common uses.
On some aircraft, selecting engine anti-ice will automatically increase the flight idle speed to insure an adequate minimum bleed air pressure reaches the engine inlets.

It is also sometimes run to the leading edges for anti-ice.

Certainly you would know your aircraft systems better than I, but it seems to me that in the planes I ride in most often (CRJ2) the cabin airflow is very much dependent on the rate at which the turbines are rotating. I feel the airflow increase and decrease as the engines are spooled up and down when taxiing, when the engines are brought back to idle for a descent, etc.

I edited my answer to say “minimum constant supply”. Different aircraft behave differently at different power settings, and I can’t speak for all aircraft. The amount of air flow will change at different power settings, but even at idle power, there must be enough flow to keep the aircraft pressurized.

Down at idle range you will feel the flow changes because the pressure regulating shutoff valve at the engine will eventually be full open to keep the duct pressure up, so any change in 10th stage bleed flow (what supplies air cond on the CRJ200) will be noticed in the cabin. But when it's modulating at higher thrust settings you don't have major flow changes as the valve keeps the bleed duct pressure at about 80 psi. regardless of the upstream pressure which will be well above that.


text:
Are cirrus clouds stratiform?
Cirrus clouds:

Are they warmer than the environment? - Cumuliform.
Or are they cooler? - Stratiform

What differences do cirrus clouds have to the "Cirro" versions of a cumulus or stratus?

All these clouds signal an approaching warm front and potentially a storm.  Warmer, moisture laden air rides over the top of cooler air, forming visible clouds while the ground level front is still many miles away.
Cirrus clouds are composed of ice crystals and form at very high altitudes.  They are the first of the approaching clouds.  Cirrostratus form as more moisture arrives and the front gets closer, followed by status.
Cirrus clouds, being the highest and first to arrive, are stratiform.
Cirrostratus are observed as broken cirrus/blue sky becomes overcast.
Cirrocumulus clouds are the result of high altitude convection and contain supercooled water.  They can transform into status clouds, and are also associated with approaching weather.  The vertical motion that creates cirrocumulus seems to be more of a transient local phenomena, such as turbulence.


text:
Is there a career path to fly fast, military jets without being in the military?
I would like to pilot or fly in fighter jets however as I have mild asthma I cannot join the Royal Air Force. So is it possible to fly in or pilot these kinds of aircraft as a career without being in a branch of the military?

You can get somewhat wealthy and buy one... What kind of "fast jet" do you want to fly? Do you just want a ride in one, there are a lot of services that do that? If you just want the experience, there are places that let you fly anything from L-39's to Mig-29's.

@RonBeyer I was more thinking about being a flight test engineer that works on fighter aircraft or somehow being able to pilot fighter jets as a career. Sorry for not being very specific.

Unfortunately people who end up flight testing (pilots and in-flight engineers) are ex-military pilots. You can certainly become a flight test engineer or test pilot, but testing out military grade equipment is left to a very elite few.

Welcome to aviation.SE! I reworded your question slightly based on the extra info you gave in your comment. If I got it wrong, you can edit again yourself or just roll it back.

Yes, any career path that allows you to earn large sums of money and self-finance the purchase, training, and upkeep for the surplus fast jet of your choice. Beyond that the civilian careers that offer fast jet opportunities are primarily only open to former military pilots.

I don;t want you flying a 'fast jet', or even a slow one, over my head if you might have an asthma attack. I speak as someone with mild-to-intermediate asthma. Even when well-controlled, the condition can suddenly flare up.

There's no likely career path, if you have serious enough medical problems they will probably prevent you from getting a job in aviation flying anything commercially. However, that's a separate question, you'd want to talk to an aviation medical examiner to find out what avenues are open to you.
There is a path to flying military style jets as a civilian test pilot, which is open to anyone, however you need a lot of experience and most are retired military.
However, with enough money you can fly just about anything, former military jets do go on the market, often they aren't that expensive to buy, the big costs are maintenance and fuel. If they are to be flown non-commercially the medical requirements are usually lower too. You need to be prepared to spend between \$800-\$6000 per flying hour, depending on the type.

Mild asthma that is completely controllable through certain inhalers etc ought not be an issue for getting any medical clearance needed for non-military aviation, other than being an astronaut.  Very analogous to people being eliminated from the possibility of military flying based on vision issues that are correctable w/ glasses, but still eligible for careers in commercial aviation.  I'd suggest that there may be some room for some improvement in this answer to make it a better fit for the details given in the question.  The answer to some parts of the question will still be "no", but...

It is possible for civilians to train for a test pilot or flight test engineer at the National Test Pilot School.

Be an adversary. Private companies now run 'Adversary" flying training where they own and operate private fighters to fly against pilots in fake engagements

Look up "Draken International" UK.

I don't know any other than Draken. These companies don't discriminate on nationality and provide NATO level service.
https://en.wikipedia.org/wiki/Air_Support_to_Defence_Operational_Training#Shortlisted_companies

This doesn't answer the question which is what is the career path to a job such as this. The reality is the pilots flying for Draken and similar jobs are filled with ex-military trained fighter pilots. As an engineer that worked with many fighter pilots I can tell you that flying a fighter is about 20% flying and 80% fighting. A modern fighter is not an airplane with some weapons on it. It is a complex weapon system that just happens to fly. The military is the only place where you can learn it all.


text:
Is there any legal way to fly an inline twin-engine aircraft with a single-engine certificate?
Is there any legal way to fly an inline twin-engine aircraft with only a single-engine endorsement? For example, if it's an ultralight or amateur built?
I understand Rutan's Defiant was an inline twin that could take off, fly and land with either the front engine, rear engine, or both.
I assume you can do this in a twin inline ultralight as there is no twin engine ultralight endorsement in USA or Canada.
I'm asking about the ultralight or amateur built categories in the USA or Canada, not the US LSA category as I understand they are single engine only.

You should specify what aviation jurisdiction you're in, because rules for ultralight or microlight aircraft vary between USA, EU, and various other places.

Long before Defiant, the Cessna Skymaster was demonstrated with either engine running (and the second at idle, for safety) on takeoff and routine flight.  Before that, a P-38 could do it, and it wasn't even an inline design.

I just noticed, you have two distinct questions here -- one concerning Defiant (and applicable to other inline GA aircraft like the Skymaster) and the other relative to microlight/ultralight.  You should ask only one question here, then ask the other separately.

the question is what categories is this legal, if any

Okay, I see tags for FAA and Transport Canada -- which have significantly different ultralight regs.  Which is it?  And you only want the ultralight/microlight question answered?

I'm asking for Canada and USA and what categories, which is probably ultralight and amateur built,  and certified  in both countries

Yes, there is a legal way to do this... Get an MEI to fly with you.

Under United States Part 103 ultralight category, with no license or aircraft certification requirements as long as the the limitations of the category are met (dry weight, fuel capacity, single seat, and level flight maximum speed, permitted flight locations), you can do anything you like.  Whether it's safe or a good idea is up to the pilot.
Last time I checked, Part 103 requires a dry weight (with engine, no fuel, no pilot) under 254 lb, no more than 5 US gallons (though actually called out in liters) fuel capacity, and level flight speed limit of 55 kt (about 62 mph).
I can't answer relative to Canada, as their regulations concerning ultralight/microlight aircraft differ from those in the USA.

What is the fuel capacity.... when the fuel is electricity? :)

USA Part 103 specifies a maximum capacity because electric flight wasn't a reality when the regulation was written.  I presume they'll get around to electric endurance limits eventually, but in the meantime, your capacity is less than ten gallons of gasoline.

So is there no electric endurance limit?  I thought the maximum fuel capacity was 5 gallons. Has this increased? I also understand the maximum weight is 250lbs, not including safety equipment.  Is a small sustainer engine safety equipment? In an emergency I'd rather have a controlled flight onto a road or clearing, or the next airport, than using a ballistic parachute to fly uncontrolled into terrain.  No better safety equipment than an extra inline engine .....

Yep, you're right on the fuel capacity.  I haven't looked at Part 103 in detail since I determined I'd never be able to afford a ultralight combined with storing/living anywhere I could fly it (no flight over populated areas like towns).  These things do glide, after all -- you won't just fall if the engine quits.  Same situation as a Cessna 150.  The parachute is for structural failure or unrecoverable attitude.

Glide like a brick, more like it. lol. like 10:1 ratio.  So if you're at 2,000 ft and your dropping at 500ft/min, you've got 4 minutes to find a spot, fly to your field of choice ( basically the one beneath you)  and do a final approach (with no go around)....

Sure, and you've got four miles radius in which to find that field, if you're prompt about looking and don't waste a lot of time trying to restart your engine (if it's electric, it's probably battery voltage cutoff anyway, and neither restart attempts or an extra motor will help you).

that's why one  needs to totally isolate the two motor systems with independent batteries, etc :)

And then you have the weight of two batteries and two motors, plus the potential confusion of advancing the locked out throttle -- KISS.  One higher power motor w/ higher capacity battery is almost certainly overall better than two.  Twin engines are used for long flight reliability or when a single engine with the desired performance is too expensive or heavy or vibrates too much for the airframe.


text:
Is it possible to fly an ultralight aircraft with a 13.4kW engine?
I want to build an ultralight within the 115kg preload (US standard). Can I use and engine with the specifications below? My weight is around 63kg.
Rated output: 13.4kW(18HP)@3600RPM

What does that engine weight?

The Wright Flyer flew with a 12 HP engine.

I think this answer provides an answer. Thus I'm tempted to flag the question as a dup.

The earliest ultralights (hang gliders with add-on engines) used engines with as little as six horsepower (about 4 kW), possibly smaller.  That said, these aircraft were originally built as foot-launched gliders, and even so had safety issues and many incidents due to poor climb rates.
The main requirements for the engine in an ultralight are climb performance (which translates directly into takeoff acceleration) and reliability.  With the correct propeller and acceptable dry weight, an 18 hp (13.5 kW) engine might be acceptable, but every additional kilo of engine mass (compared to engines built for lightness) is one less kilo of structure, and the RPM figure given seems to point to a four-stroke engine, which will generally be heavy for its power output as compared to the two-stroke type.
Four-stroke engines have been used in larger aircraft for more than a century, but those are mostly engines designed and purpose-built for aircraft use.  An engine designed for garden or yard equipment, generator, or compressor service will usually be heavier.  You'll have more trouble finding an optimized propeller for 3600 rpm than for 5500, in that power range.
In the end, if that's a cast iron four-stroke engine, it's unlikely you'll make your overall dry mass budget to stay within US Part 103 requirements without compromising structure, and you're likely to see performance issues with minimal power and maximum takeoff weight.

thank you sir, thats really helpful.

A good example of an early and underpowered design was the Weedhopper, which was often equipped with cast off engines and had a bad reputation. The design came into its own when it received the 26 hp Royal 228 and has since sold some 13,000 examples.


text:
Can a private pilot land at any category of airport?
I'm aware that commercial pilots require special training for landing at Category C airports (e.g. Innsbruck), but I was wondering if, as a private pilot I could land at an airport such as this, whitout training provided I feel comfortable enough to do it.

Since you mention Innsbruck, are you asking about EASA regulations?

@Pondlife Yes, I am. I maily interested in Tromsø Lufthavn Langnes in Norway.

At least these four airports (NO) you can fly in a private aircraft.

@LukeDunkley I have landed already in LOWI with a TMG. No restrictions or additonal training required, just regular VMC entry into the control zone and landing on the runway. Normal landing fees. All fine and dandy. :)

Categories are for commercial pilot operations, they don't apply to private pilots, so there's no inherent regulatory limitation to flying into a Category C airport. The regulations say commercial pilots must be appropriately trained, and airlines have specific rules internally for this and say who can land at them, i.e. captains only or not.
A private pilot can land at any of these, provided the airspace and airport rules allow it (see @LittleCode's answer for some of those), it's up to the pilot's judgement to train themselves. Keep in mind that for many of these airports the special challenges of landing or departing for a light aircraft are mitigated due to much slower approach, takeoff and landing speeds, especially in visual flight conditions. In instrument conditions these airports can be very challenging to get into or our of, but you can still do it if you have an instrument rating, currency and the guts to do it.

Thanks for the answer.

Generally speaking, the short answer is "probably not" (I don't know Innsbruck).
Long answer:
If you look into it (as a private pilot, you should know "how" already), you will most likely find that there will be a number of obstacles in your path at the majority of large airports.
These obstacles can include (but are not limited to) :

Airspace restrictions (both local area and at the airport itself) so, for example, you might need IR rating and a suitably equipped aircraft.
Technical limitations for your aircraft (e.g. your aircraft might not be able to meet speed requirements)
Airport prohibitions, for example Heathrow publish the following:

Flights for recreational, commemorative, charity and record breaking
purposes, light twin engined private aircraft and all light single
engined aircraft will not be permitted to use the airport. 'Light
aircraft' shall be defined as any aircraft that has a maximum gross
take-off weight of 12,500 lb (5,670 KG) or less.

And even if the immediate technical obstacles don't apply, you might find commercial obstacles such as (but not limited to) :

The requirement to nominate and use a handling agent for ground ops
Very high landing fees

Note that this is specific to EASA (as per question tags), it's different in the US and other countries not part of EASA.

Its "different" how exactly ?  It doesn't matter if you are in the US or Timbuktu, you still have to give due consideration to all of the same factors I outlined above ?  Airspace restrictions, airport rules, airport fees ... same things to consider the world over. "How" they are implemented may be different, but the basic premise of having to consider the same things is the same.

For example, I can fly into ORD as a private pilot (coordinating with ATC first). Also nearly all class C airports in the US are perfectly fine with GA traffic, no special training required (as the OP suggests). Landing fees are not that prolific here either and most, if not all, have a GA ramp where you don't have to "nominate a handling agent". If this question were focusing on the US, the answer would probably be "probably yes" instead of "probably not".

Thanks for the answer. I wasn't mainly asking about large airports in general, but those more commonly considered dangerous (Samos, Innsbruck, etc.)

@LukeDunkley There are some challenging airports in the US, but none that the FAA considers dangerous enough to require special training for GA pilots or ban them entirely. Congestion is another story, but we can easily fly GA into even major airline hubs if we’re willing to pay the fees. Things really are different here.

I think this is confusing "Category C" (difficult/special airports like Innsbruck, or say Aspen  for a US example) with airports that are simply busy

@UnrecognizedFallingObject: AFAIK, in the US the busy airports aren't dangerous (except for having lots of traffic), while the airports that are somewhat dangerous, or at least require special training & equipment, are far from busy.  I wouldn't recommend flying into Wilson Bar (Idaho), for instance: http://www.airnav.com/airport/c48

If you have questions regarding the specific Airport it is always better to check in AIP. For Innsbruck, for example, VFR (most of the PPL pilots), Airspace D, and no restrictions mentioned in Airport info, so yes it is allowed.
And you can find Visual Approach Chart in AIP.


text:
When can I proceed inbound in a hold in lieu of a procedure turn when cleared for the approach?
Let’s say I am holding on a published hold in lieu of a procedure turn but not yet cleared for the approach. Upon receiving approach clearance (say on the outbound leg of the hold) would I have to cross the fix an additional time before proceeding inbound?
I have attached a picture as an example and a red X where the approach clearance is received.

I'm a little confused at your question. As ATC, if I issued the approach clearance when you were at the red X, I would expect you to continue on the outbound leg, turn inbound, and cross HXO inbound to the runway. Are you asking if I would expect you to do another full hold after receiving the approach clearance? (I would not.)

You can always request a "victory lap" if you want to do one more turn around the pattern!

You don't need to do a full turn around the holding pattern, you can just cross the IAF and proceed inbound. This is from the AIM 5-4-9(a)(5):

The holding pattern maneuver is completed when the aircraft is
established on the inbound course after executing the appropriate
entry. If cleared for the approach prior to returning to the holding
fix, and the aircraft is at the prescribed altitude, additional
circuits of the holding pattern are not necessary nor expected by ATC.


text:
Should I do bachelor first or pilot training first?
I am a student now going to grade 12 residing in Nepal. I am perplexed about should i do my training first  get a job and do bachelor alongside with my job or should I do bachelor first and then training and then get a job.

If you have ready access to university, do the degree first. You won't have time later, and if you get a pilot job in future and lose your medical for whatever reason, you will have an education to fall back on.  In any case, the aviation industry is going to take a number of years to recover from this whole "plague" fiasco, so you shouldn't be in any hurry to get a pilot license.  Thousands of pilots are on furlough and will likely continue to be for quite a while.
Long term, the future is bright, but get a degree first.

If possible, apply to a college which has a flying club open for students. You'll get ground school, flight training, and flying time at a discount and you can pace your progress according to how much free time and money you have.


text:
How does the radio altimeter reading change with the bank angle?
How does the radio altimeter reading change with the bank angle?
Following example:
Let's say, we're flying at 1000' AGL and a bank angle of 0° above a endless flat surface. The radio altimeter shows 1000' as well.
Now if we roll to either side to a bank angle of 10° and maintain 1000' AGL, what does the radio altimeter read now?
Does does the radio alt increase accordingly or is the radio altimeter adjusted to always face down?
I'm especially interrested in the way how Airbus handles this situation.

The RA antenna emits and receives signals in a cone approximately 60° wide (I think). The RA shows the distance to the closest object in that cone. Up to 30° bank (and pitch), RA should still work and show 1000ft in your scenario. Comment instead of answer, as I can’t back it up at the moment.

The Rad Alt will show the same value of 1000'.
The radio altimeter antennas provide a radiation pattern that covers at least +/- 15 deg in pitch and +/- 20 deg in roll, though most cover more - typically +/- 20 deg in pitch and +/- 30 deg in roll.
The transmitted signal fans out equally over the entire pattern area from the transmit antenna and is reflected back where it is received by the receive antenna. The returned signal is spread over a short period of time due to the varying distances the signal must cover. The closest point will be the first received. As the aircraft changes pitch or roll, the location of the closest point will move within the pattern, but the shortest distance will still be the same.
The DSP software also processes the signal to filter out smaller objects such as the approach lighting towers.


text:
Which regulation requires me to report entering a hold?
I have seen in many bulletin boards that a pilot is supposed to report upon entry into a holding position.
I can find that reporting nowhere in the regulations .
I can find in the regulations where a pilot must report leaving a hold at expected clearance time,  and at that time he is supposed to report time, altitude, and position, and the fact that he is leaving the holding position.
Where in the regs does it show that you must report upon hold entry?

Which country or regulations are you asking about?

So, this is found in the AIM, para 5-3-3 (a)(1)(f) (PDF), assuming you're asking about FAA regulations.

5-3-3. Additional Reports
a. The following reports should be made to ATC or FSS facilities without a specific ATC request:

1. At all times.

[...]
(f) The time and altitude or flight level upon reaching a holding fix or point to which cleared.
(g) When leaving any assigned holding fix or point.

Now, the AIM is not regulatory. It uses terminology like "should" instead of "shall", which lawyers will happily jump on, and it in fact says this about itself:

This publication, while not regulatory, provides
  information which reflects examples of operating
  techniques and procedures which may be requirements
  in other federal publications or
  regulations. It is made available solely to assist pilots
  in executing their responsibilities required by
  other publications.

AIM guidance is to report arrival and departure of a hold. Talking with controllers, they don't want to hear the reports, especially when things are busy, in a radar environment.  But the AIM doesn't say that.
If you are in a non-radar environment, you must report arrival and departure from the hold. If you are in a radar environment, most controllers in the US do not want a report, but the AIM does not provide that guidance.
I always report entering a hold, except when practicing VFR holds in a radar environment.
As far as I know, there is no definition of what "established in the hold" means.
To address your specific question, I am unaware of where in 14 CFR hold entry reporting is mandated.  However, much of the "rules" (really policy) about IFR flight are in the Instrument Flying Handbook and to a lesser degree, the AIM. And in my experience, ATC may ask for a report upon entering a hold.

Hm. Given that 5-3-3(a)(1) is the "at all times" reports, and not the "when not in radar contact" section, are you sure that reporting reaching a holding fix or clearance limit is somehow exempt when in a radar environment?

My reading is that the at all times is for mandatory reporting points, which are depicted with a solid triangle on US charts.

But I agree the AIM states upon reaching or leaving a holding fix.  Looks like I will have to make a few phone calls, and get enlightened.

Well, phone calls are never absolute authority, but the local approach controllers say no reporting into or out of a hold.  My buddies at the FSDO say the AIM is the bible, and it says report at all times.  But they acknowledge that the controllers simply don't want those reports, especially when they are busy.  To their knowledge, there has never been an enforcement action on this matter. There is no specific rule, except following FAA policy in the AIM.

I'm sure you're right - but OP is likely asking because he's prepping for a checkride or something, and while enforcement action is unlikely, a busted checkride is possible. As far as My reading is that the at all times is for mandatory reporting points goes — I respectfully disagree; those are covered quite explicitly in 5-3-2. Note (b) in particular, where it describes the chart depiction. :) 5-3-3 is additional reports, eg, in addition to those in 5-3-2. I'm not surprised that ATC says "don't bother", based on their bored "roger" responses whenever I report crossing the holding fix.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Do you need a commercial certificate to fly unpaid for a non-pilot owner?
Let's say that an aircraft owner is not a pilot and needs someone to fly an airplane for him. If the owner pays 100% of the costs for the flights but does not pay the pilot, does the pilot require a commercial certificate?

It's not completely clear what you are asking.  Are "he" and "you" the same person?

Try using "the owner" and "the pilot" instead of "him", "I", and "you".

I reworded your question to what I think you're asking, but if I got it wrong please just rollback or edit again.

This situation would be Illegal as the law stands. What it boils down to is that flight time is considered compensation. This answer covers it well and in your case, since you are not paying your pro-rata share and the owner is paying the full expenses you are in a way getting compensated in flight time.
This answer is somewhat related as well and its seems there needs to be some "common purpose" for everyone on board as well.

I think there is an important distinction between "flight time is considered compensation" and "flight time may be considered compensation".  Flight time is not automatically classified as compensation; but it can be, if it was a primary motivator for a flight.

@abelenky I agree and was thinking while I was reading this that a better way to describe it would be that flight time generally provides a benefit to the pilot (particularly if they have a relatively low amount of flight time which needs to be built up in order to be competitive for a job).  The FAA considers this benefit to be compensation if someone else pays for it (exact interpretation is in the linked question, which is really a duplicate).

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Can anti-radiation missiles be used to target stealth fighter aircraft?
What I understand is that anti-radiation missiles are accurate and long range.
So, assume that a fighter aircraft is 100% invisible on radar. However, its radar is transmitting energy continuously which can be detected and targeted using anti-radiation missiles. As Wikipedia suggests there is Russian air-to-air anti radiation missile (Vympel R-27EP).
Wouldn't such a missile neutralize the stealth technology? And why don't we have any other examples of such weaponry other than Russian one?

"assuming that a fighter aircraft is 100% invisible on radar. However, its radar is transmitting energy continuously which can be detected" - that's contradictory: anything emitting radar is detectable by another radar receiver, not just things reflecting radar signals.

Echoing @Dai : a plane that's radiating is -- **by definition -- visible to radar, and not stealthy.

Guys, stealth aircraft essentially don't use radar.  (Sure, they turn it on when near home base in the US, etc.)

(Actually it looks like the F117 doesn't even have a radar.)

"anything emitting radar is detectable by another radar receiver" that's just not really true or sensible.  It would be much like saying "Any pushbike can definitely get away from any car."

This question doesn't make any sense to me. "Assume a ninja is 100% undetectable, but if he is constantly screaming wouldn't you be able to detect him?" I mean, sure, but why are you assuming the ninja is screaming to begin with if he is trying to be stealthy?

@Fattie Anything emitting radiation of a specific wavelength is detectable, at some distance, by a receiver of radiation of that wavelength. Does that make more sense now?

There are many anti-radiation missiles in many arsenals, they are designed for air to ground missions, attacking surface to air missile radars from a long distance. I don't know whether it would be possible for an anti-radiation missile to hit an air target.
If we assume it is possible your idea has a significant flaw in that stealth aircraft turn off their radars when they are on a stealth mission. Running a radar is like holding a flare in the middle of a field on a dark night, which is why they don't do it, at least not using conventional radars.
Some stealth airplanes don't even have a radar, for instance the F117. Typically attacks were done using GPS for precision navigation to the target, which is then attacked using precision munitions like laser guided bombs or GPS guided bombs or missiles.
Nowadays here are advanced radar systems that spread signals over multiple frequencies which will blend in with other signals, and can be directed in specific directions to avoid being detected. If a radar beam isn't pointing towards a sensor then the radar won't be detected.

Comments are not for extended discussion; this conversation has been moved to chat.

If the stealth aircraft's radar were continually transmitting, then, yes, the other stealth features would be completely useless, and missiles would easily home in on them and shoot them down. Which is why the radar on stealth aircraft are very rarely used.
Anti-radiation missiles are much more dangerous against ground radars precisely because they are in a fixed position. If the crew turns off the radar, then the missile just has to remember where it last saw the radar, and attack that point. The same can't be said for an aircraft's radar, because they are by definition mobile. Thus an air-to-air missile would have to rely on the element of surprise, basically sneaking up on the enemy plane so they don't realize they're being attacked (and thus have a chance to turn off their radar) until its too late. Which means in turn that its usually better to keep the radar off all the time unless you have some specific need for it, and even then, use it as sparingly as possible.
Note that the same is true, albeit to a lesser extent, for non-stealth aircraft. You can detect another aircraft's radar from a lot further away than it can detect you, so if you have the radar on all the time, you're basically advertising your position to an enemy that you might not even be able to detect. So the only time military aircraft use their radar is if they know they've already been spotted, if they're deliberately playing dumb to act as bait for an ambush, or if they judge that giving away their position is an acceptable trade-off for greater awareness.

Wording nitpick: "airborne" could include a tethered balloon (to see over nearby hills), so the definition of airborne doesn't actually require "mobile".  It does for aircraft radar, though, even including a stealth helicopter: if getting shot at, it wouldn't hover in place.

Re: "acceptable trade-off for greater awareness" - in the case of AWACS, that's the awareness of all friendly units in the area, and carrying a huge powerful radar is one of their main purposes.  So I'm guessing those military aircraft leave their radars on most of the time.  (And don't fly over hostile territory that hasn't been cleared of air defenses.)

@PeterCordes Good point on the wording, I'll edit it. And, yes, the whole point of AWACS or similar aircraft is to have their radar functioning, so their radar is typically on most of the time when they're on station. But, of course, if enemy fighters get to close, they certainly have the option of turning the radar off and running away.

"Anti-radiation missiles are much more dangerous against ground radars precisely because they are in a fixed position" - unless the radar is mounted on a ground vehicle (especially one that's constantly moving).

Yes, but such aircraft can turn off their active emissions (radar, EM jammer, communications etc etc.). And AESA radars can be very select about in which directions it emit to not make the aircraft detected to known threats.
There is also missiles with Home on Jam capabilities. So if you jam to disguise your position for example, such missiles can home in on the jamming signal. So as a stealth aircraft, it is probably another thing to keep turned off unless you really need it.

It's not uncommon to use dedicated jamming aircraft alongside the stealth aircraft, e.g. the F-18 Growler.

I don't have rep to comment, so this answer is more of a side note, that stealth fighters have been trackable for decades. The TAMARA radio system from what was Tesla Electronics (former Czechoslovakia) involved a large network of receivers that could correlate reflections from radio signals, and also identify the communication between onboard weapon systems, if I recall correctly. https://en.wikipedia.org/wiki/Tamara_passive_sensor I do remember the Czech premiere appearing in the UK giving assurances to Western powers that Tamara would not be sold because Tesla was to go bankrupt. I think that is what ended up happening.
It's successor VERA is apparently also able to track stealth planes https://en.wikipedia.org/wiki/VERA_passive_sensor
So while it is unrelated to the question of anti radiation missiles, anti radiation missiles are probably not as useful if you have these radar systems already

These "passive RADAR systems" have received an "upgrade" in recent years which improves performance quite a bit. The idea is to scatter lots (millions!) of low power transmitters all over a country. Since stealth aircraft are optimized against horizontal RADAR signals, vertical radiation from lots of ground-level transmitters if rather effective. In the UK, I estimate that about 80 millions of these devices are currently operational (for comparisons, the UK population is about 67M). Here's a Wikipedia article about these transmitters: https://en.wikipedia.org/wiki/Mobile_phone

This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. - From Review

@Klaws The other thing that makes me rather suspicious that these systems are more effective than presented, is that Wikipedia and other online sources don't mention anything of other capabilities that I was verbally presented by someone with first hand knowledge of the system (either selling or building them I don't recall). Apparently they don't just correlate bounced signals but also employ a range of signal analysis tricks, including being able to detect chatter between onboard computers in different systems (eg: bomb to control or something like that)

@Ralph J Both Altern's and your notes/comments are valid. Altern mentions that he is not allowed to comment, so he posted his note as an answer. I think it adds to the understanding of the underlying issues, so it should not be deleted. Maybe Altern can "beef it up" by turning it into a relevant answer - like by addressing the last paragraph (the emissions are used to coordinate CAP to attack with better suited types of missiles).

As an addition to other answers:
To form a picture of the battlefield situation, the radar system of a stealth aircraft (or any radar for that matter) does not need to transmit all the time. It can blib or burst a signal, or perform a sweep for more resolution, and then hibernate. It can also "listen" to other radar signal sources and echoes and thus image the surroundigs to some extent.
As explained in other answers and especially in the comments, modern warfare is no longer a game of separate units. It is a merged system, and on the NATO side, the "glue" of this matrix is the Link 16 network.  Data collected from multiple sources is trasferred via Link 16 and is used to form a very comprehensive and accurate realtime presentation of the battlefield.
The stealth aircraft, or actually any networked battlefield operator has eyes, ears and noses all over the place, they really do not necessarily need to use much of their own. For example, for an F-22 or F-35, information about enemy precense is initially delivered from elsewhere, and they only need to use their own radar to perform a strike, and maybe not even for that. Should the adversary fire the missile in question at them while they were using radar, they can simply switch off the radar transmitter, and they have become invisible. The enemy missile only has their last tx position, and that just won't be of any help.

In theory - yes. In practice - I dont think so.

The aircraft should emit radar wave easy to detect - won't remain stealthy anymore. Rare case, improbable.
Most of the ARM's software and flight profiles are optimized for hitting ground targets, not very agile. So the chances for hitting the aircraft  are very low.
To make a significant damage to in-flight aircraft you have to use high explosive fragmentation warhead with proximity fuse. Maybe some of the ARM have ones, but lool at 1) - they may not be optimized against aerial targets.
Intercepting the aerial target means different computing algorithms than against ground targets.

Conclusion: I don't think so.
There are some indications that some of air-to-air missiles have passive guidance mode but I have never heard about combat engagement using such a mode.


text:
Where can I find maintenance manuals for the A380?
My friend recently acquired an external green light from an A380. They are the only details i have from him. I tried hunting the internet for maintenance manuals, technical details, schematics, basically anything i can think of. Apart from a couple scam websites selling Haynes manuals, i came up with nothing.
Does anyone know the power requirements for the lights or, ideally, a document that lists aircraft details and specifications. I imagined that maintenance details will be available, but nothing came up.

You’re going to be looking for the Airbus Illustrated Parts Catalog (IPC) for the A380 airplane.  It’s something I’m sure you can request from Airbus, but it’s gonna cost you.


text:
Why is this airplane flying in circles randomly?
This G650 has been flying around for over an hour now.  Is this somebody with a mechanical problem who is burning fuel before returning to their airport of origin?

Your question reminded me of https://xkcd.com/1910/ :D

What you observed is probably a Gulfstream production test flight, either an initial or a snag clearance flight, or possibly a Customer Acceptance from Savannah Air Center, which is a completion center across the ramp from Gulfstream. It could be possibly an experimental test flight if Gulfstream runs experimental flying from Savannah (I think they have a test operation in Wichita), but production flights are far more common.
The manufacturer will have designated test areas by agreement with the appropriate ATC units, with specific boundaries, and they will flight plan into the test area for production test flights (aircraft coming off the line) where a Functional Test Procedure, usually taking several hours to complete, is performed.  The ATC clearance will be to maneuver anywhere within the test borders, with a block altitude clearance they are free to operate within, until they need to go higher or lower for different tests and request a new block.
The pilot flying will be steering this way and that pretty much randomly, within the test area borders, while the other pilot performs systems tests, and the two of them will do a number of flight tests where they operate the airplane to, but not beyond, it's certification margins (things like stalls, engine shutdown/relights, yaw damper function, anti-ice tests, those sorts of things).
The airplane will return with or without snags, and the plane will get snags cleared, and go back out for another flight to check the snagged items.  On a corporate aircraft it'll then go on to a Completion Center (usually a separate company selected by the buyer for high dollar corporate a/c) for the interior.
Once the completion Center is done the interior, the customer or a customer's agent is taken on a Customer Acceptance flight before accepting the a/c.  They will go through the cabin to make sure everything is perfect in the cabin, both fit and system wise, getting it fully cold-soaked to make sure valves don't freeze, and subject to pressurization changes that can make interior panel joints open up (and I mean perfect - the slightest flaws in panel fits will be snagged).

Gulfstream does a lot of its flight test work in Savannah and also has a facility in Roswell, NM for this as well.

I'm a little surprised that they do this kind of thing directly over ca. 100,000 people. Why not pick a quieter spot?

What's an a/c in this context? Aircraft?

Production flight test is not considered really "high risk" the way Experimental flight test is, so test areas don't need to be remote.  The airplanes don't yet have a C of A issued and are under a flight permit, but are not being operated outside of certification limits.  You can expect that there will be several areas designated. Which one is used on a given day will be based on traffic requirements.  At my company a flight would file for one of 4 test areas and ATC would issue a clearance for that one, or one of the others if they needed to run a lot of traffic through the filed one.

@Mast yes a/c is a common abbreviation.

@Strawberry - Short of going out to sea, there aren't too many areas that large around Savannah or in fact on the eastern seaboard that aren't over populated areas.  And if you did need to make an emergency landing for any reason, you'd want to be close enough to an airport (or better yet several airports) to be able to do that, which rules out testing over the ocean.

@Mast Thanks for asking that, I thought they were talking about air conditioning!

I used to work at an aircraft manufacturer on the coast in Lancashire. They make fast jets. Sometimes they did test flights that were so good to watch that we all stopped to gaze upwards, including traffic on the main road. People got out to watch and caused traffic jams.

@JohnK It is not dangerous and I do not think Mast implied that. But it surely does generate noise.

The fact that it's near Savannah and tracking within a confined airspace, I'm fairly certain this is a flight test being carried out by Gulfstream.

What makes you think it is doing loops?

@MichaelHall must be one heck of a test flight :)

@MichaelHall I don't mean vertical loops. It's just tracking within a confined a confined airspace.

@JZYL, The word loop means a vertical loop...  (horizontal loops are called "turns")   I like your short, simple and to the point answer, but it perpetuates incorrect terminology unless you edit it.

@MichaelHall Thanks for pointing it out

@MichaelHall Just to clarify, the word loop in reference to aircraft maneuvering is vertical.  In general the word loop can definitely be horizontal.

@JMac, yes, your shoelace loop can be horizontal.  But this is an aviation website and the question was about an airplane maneuvering, I really didn't think further clarity was needed...

I would second what John K said, it’s most likely a GAC factory flight test or demonstration flight.  Also with the airplane identified as GLF6 and, most likely going be the call sign “Gulf Test six” would pretty much confirm that suspicion.  You will also see similar flights down to Brunswick Golden Isles airport (KBQK), as Gulfstream does a lot of flight test work down there as well.

Indeed, is it slightly strange that test area is overa big population?

@Fattie, the sort of flight test they'd be doing here isn't dangerous.  The Gulfstream is an established aircraft model, so it's well-known how it handles and most of the ways that it can fail.  If they were doing something that carried a non-trivial risk of crashing, they'd be doing the test flight from an airport further west, with nothing but cows and wheat fields to hit.

I guess it's more of a "test drive!" than what we think of from action movies as a test flight!  ... heh

@Fattie -- yeah, production test flying has far more in common with post-maintenance functional check flights than it does with experimental or even certification test flying

authors: Vladimir F Героям слава


text:
What exactly are these unusual flight code names that require ATC priority?
(Related to this question)
The FAA's ATC Orders section 2-1-4 lists a number of different flight types that should get priority handling when possible. The obvious candidates are all mentioned: emergency services, VIP flights, search and rescue etc. But these less obvious ones are listed too, what exactly are they?

NIGHT WATCH aircraft
Aircraft using code name FLYNET
Aircraft using code name "Garden Plot"
Special Air Mission / SCOOT flights
OPEN SKIES Treaty flights

FLYNET, isn't that just a euphemism for Skynet? Also, if you get a call in from someone's flying Garden Plot, you'd better give it some priority! ;)

Night Watch may refer to the E-4B 747 platform used as a command/control center when the President/Vice President are not on board. FLYNET is for aircraft transporting a nuclear/chemical disaster team. I think Garden Plot is a defunct program to restore civil disturbances.

note that for #4 Special Air Missions, flights will usually have call signs of SAM---

Night Watch is only applicable for the airport at Castle Black ;)

NIGHT WATCH / NAOC
Night Watch or Nightwatch is the program identifier for the USAF National Airborne Operations Center (NAOC), including at least certain Boeing E-4 flights.
NAOC (used in flight):
From JO 7110.65W:

The term “NAOC” will not be a part of the call sign but may
  be used when the aircraft is airborne to indicate a request
  for special handling.

FLYNET
From JO 7110.65W:

The code name “FLYNET” indicates that an aircraft is
  transporting a nuclear emergency team or a disaster
  control team to the location of a potential or actual nuclear
  accident or an accident involving chemical agents or
  hazardous materials. It is in the public interest that they
  reach their destination as rapidly as possible.

GARDEN PLOT
Classified. Related to operation Garden Plot. Presumably a callsign to be used by aircraft as part of that operation.

SCOOT
Term related to Special Air Mission flights in evacuation of government VIPs.
From JO 7110.65W:

The term “SCOOT” will not be part of the call sign but may
  be used when the aircraft is airborne to indicate a request
  for special handling.

OPEN SKIES
Callsign for observation aircraft under the Treaty on Open Skies. The USAF aircraft used for this purpose is the OC-135.
From Wikipedia's Treaty on Open Skies:

Observation/Demonstration flights are conducted
  under rigid guidelines outlined in the Treaty of OPEN
  SKIES that govern sensor usage, maximum flight
  distances, altitudes and priorities.

It might be worth noting that an Open Skies aircraft will be a foreign, probably Russian, aircraft. The OC-135 would be used over Russia. USAF doesn't have much need to invoke open skies rights in US airspace.

@Hugh I agree, that is worth noting. USAF Open Skies aircraft would most likely be operating over the foreign soil of other signatory nations, though these aircraft could conceivably depart from, transit, or arrive in FAA controlled airspace using the Open Skies callsign. Likely the majority of Open Skies callsign aircraft operating in FAA controlled airspace would be those aircraft operated by foriegn nations including the UK, Germany, Russia, etc.


text:
How is the phraseology of IFR clearances different between the US and Europe?
In this question, a comment says that the phraseology of IFR clearances is very different between Europe and the US:

especially the VFR phraseology (but not only) is really different in
  europe and the US. If we just take the IFR clearance into
  consideration the differences are huge

What are those differences, at least the main ones?

In the US we say "point", like "one two zero point two five". They say "decimal". So weird.

My guess is that's because in several European countries, point is the thousands separator, and comma is the decimal separator. So, for example, in the US, "one point zero zero one" is a little over one, whereas in Germany, it would be a little over one thousand. Thus, it's probably a good idea to just not use any of those two words.

It's not only the IFR clearance, in Europe (where ICAO regulations are used everywhere) the phraseology is very different to the one in the US.
In Europe the phraseology is clearer and easier to understand, in the US it's shorter, less formal but easy to misunderstand.
Some examples are:

118.350
  FAA: one one eight point three five
  ICAO: one one eight decimal three five zero
Holding over DKB:
  FAA: Hold over DKB to the west.
  ICAO: hold over DKB as published, FL90

To answer your specific question about the IFR clearance:
In America an IFR clearance would sound like this:

American 590, Ft. Lauderdale clearance delivery, cleared to Atlanta Intl' Airport, ARKES1 departure, then as filed, climb via the SID, expect FL320 onezero minutes after departure. Departure frequency 126.05, squawk 5523.

According to ICAO (specifically german phraseology):

American 590, Frankfurt Delivery, startup approved, cleared to Atlanta aerodrome via DKB8S departure route, flightplanned route, climb altitude 4000ft, squawk 1000

So to sum it up, what's different are the parts "flightplanned route", "climb via the SID", and the departure frequency. If it comes to vectored departures it gets even more different, as in the US the clearance just states "via radar vectors" whereas in Europe the whole vectored departure procedure is inside the clearance ("... via vectored departure, after departure runway 18 climb altitude 4000ft on runway track, passing 3300ft proceed direct DKB, flightplanned route, ...").

I almost always hear "as filed" or "then as filed" in a US clearance delivery. But I don't see this compared to "flightplanned route" here.

@MichaelHampton I don't understand what you are trying to say.

Here are several sample clearance deliveries from KJFK. Note that in many of them, the phrase "as filed" is used, instead of "flightplanned route".

Yes, that's why I indicated the difference to the German "flightplanned route"

The difference between "fligthplanned route" and what?

"as filed". It's only about the phraseology, not the meaning behin the phrase!

Again, I do not see "as filed" in your answer! This is why I left the original comment.

Oh now I get your point. I pointed out something in my conclusion that wasn't in my original example. Thank you!

Thanks for answering, especially since it was your comment! But I have to say, these differences don't seem "huge" to me: the European clearance is close enough to the CRAFT format that a US pilot shouldn't have any difficulty with it (that's a good thing, obviously). Also, I fly in the US and I've noticed that I sometimes say "decimal" when I'm task-loaded because I learned to fly outside the US (primacy in action!) but no controller has ever commented or misunderstood.

Yeah I understand what you are trying to say. You would understand it better if you would fly in Germany and are used to use the german phraseology. For me as a german pilot the phraseology as a whole is a REALLY big difference, even the startup clearance. Maybe for you it's not such a big difference as the US phraseology is way more relaxed and maybe differs from airport to airport, but here it's ALWAYS the same, as only clear. limit and dep. route change (in the US it would be also dep. freq. and the altitude to expect). We didn't even talk about VFR yet which is an own world over here in DE


text:
How many emergency/abnormal checklists are there for a typical airliner?
(Related to, but hopefully not a dupe of, this question)
The latest NASA ASRS newsletter includes the case of an A320 crew that forgot to retract the gear and started detailed troubleshooting without noticing that the gear was still down. The captain said in his report that:

I instructed the First Officer to coordinate landing at the divert
  airport while I briefed the Lead Flight Attendant and then performed
  the Airframe Vibration Checklist

The mention of an airframe vibration checklist caught my attention because it's such a specific scenario. So, excluding normal operations, how many checklists does a typical airliner (like the A320) have for unusual/abnormal/emergency scenarios?

How many checklists does a typical airliner have for
  unusual/abnormal/emergency scenarios?

Many. A book. The abnormal checklists usually compile to a book and it is located in the cockpit at all times.
As an example, there are 452 pages on the QRH of the Boeing 737. I counted 212 abnormal checklists using the index pages.

You can take a look here to get a nice idea of some of the published ones (Im sure there are more, I'm still looking for a link to them). In general check lists exist for cases the manufactures may anticipate or unfortunately may have encountered in testing or operation. Some checklists may also stem from sub makers who built individual components like the engines or flight systems.


text:
How much is airspeed reduced on an A10-Warthog when firing its cannon?
I just read on reddit that you could use the recoil of the gun as the propelling force for the A-10 if pointed backwards. There is also a question here on Aviation.SE, saying that the gun has the same power as one single engine.
I'm now wondering how fast airspeed actually decreases when firing the gun.

Let's suppose the aircraft is in level flight with no acceleration in any direction. The gun is now being fired. What acceleration is being applied to the aircraft (In m/s or kt/s)?
Bonus question: If there was infinite ammo and nothing like gun overheat, how long would it take to slow the plane down to stall speed, if initial speed was a usual A-10 speed.

FYI, reddit came second: https://what-if.xkcd.com/21/

Suggested additional bonus question: Could it take off while firing the gun?

So you're basically asking "What is the airspeed velocity of a gun-laden warthog?"

So much "clever" in these comments. Good job. :-)

At 300 knot cruise, 23,000 kg (MTOW) = 3.5e6 kg*m/s, 13,000 kg (empty) = 2e6 kg*m/s. All 1350 projectiles, 0.4 kg each, at 1000 m/s = 0.5e6 kg*m/s. So in a vacuum, you'd lose a fair bit of speed, more than I expected.

@JollyJoker: Wouldn't it run out of ammo well before the reduced acceleration became an issue?

@Sean It's just a theoretical question.

Kt/s could be units of deceleration, but m/s couldn't be.

Initially, the aircraft flies with constant speed and the engine thrust equals the aerodynamic drag. Then the gun starts to produce negative thrust. The answer would be really easy if all forces stayed the same until the aircraft comes to stall speed, but of course this is not the case. We can't just compute the deceleration at time = 0 and project that into the future: the aircraft slows down because of the recoil thrust, therefore the aerodynamic drag reduces because it is a quadratic function of airspeed. But the propelling thrust is still the same. Deceleration changes constantly as a function of time as well.
It's a complicated situation that can be worked out not with high school physics but with differential equations, in which perhaps only a mathematician will find delight. But it can also be solved with a numerical solution: a real-time computation of the aircraft state. This is what flight simulators do, at every clock tick they update the aircraft state with the latest data.
The method to do this for this question, is:

Find the aircraft data. In simulators used for pilot training, this data is supplied by the manufacturer, or from an actual aircraft rigged out with transducers. In our case, we can deduce the aerodynamic constants that we need from Wikipedia.
Take an initial speed, work out the thrust required for trimmed flight, then at t=0 subtract 50,000 N recoil thrust from the gun. This results in the initial deceleration, say -2.78 m/s$^2$
The next second, t=1, the initial speed has decreased with 2.78 m/s. Compute the new drag at this speed. Thrust is still identical to that at t=0. At the lower drag, we find a lower deceleration value, say -2.66 m/s$^2$

1. Aircraft data from Wikipedia:

Powerplant: 2 × General Electric TF34-GE-100A turbofans, 9,065 lbf (40.32 kN) each. 80,000 N total.
Maximum speed: 381 knots (439 mph, 706 km/h) at sea level, clean. Equates to 196 m/s.
Weight: Loaded weight: 30,384 lb (13,782 kg) Anti-armor mission weight: 42,071 lb (19,083 kg).
Wing area: 506 ft² (47.0 m²)
Wingspan: 57 ft 6 in (17.53 m). So aspect ratio A = $b^2/S$ = 6.54

At maximum speed, level flight, sea level, clean config, 18,000 kg, the aerodynamic lift coefficient $C_L$ and drag coefficient $C_D$ are:
$$C_L = \frac{2\cdot W}{\rho \cdot V^2 \cdot S} = \frac{2\cdot 18,000 \cdot 9.81}{1.225 \cdot 196^2 \cdot 47} = 0.16 \tag{1}$$
$$C_D = \frac{2\cdot T}{\rho \cdot V^2 \cdot S} = \frac{2\cdot 80,000}{1.225 \cdot 196^2 \cdot 47} = 0.072 \tag{2}$$
$$C_D = C_{D_0} + \frac{{C_L}^2}{\pi \cdot A \cdot e} \Rightarrow C_{D_0} = 0.072 - \frac{{0.16}^2}{\pi \cdot 6.54 \cdot 0.8} = 0.07\tag{3}$$
2. Trimmed horizontal flight
We use the aerodynamic constants found under 1. for computing lift, aerodynamic drag and thrust (which equals drag).

Take a weight: 18,000 kg, close to an anti-armour mission.
Take a speed: maximum speed = 196 m/s.
Procedure: compute $C_L$ from equation (1), then compute $C_D$ from equation (3), then compute initial drag from D = $C_D \cdot \frac{1}{2} \rho V^2 \cdot S$. This is also the engine thrust because the aircraft has constant velocity.

3. Open fire: the cannon produces 50,000 N reverse thrust

Image above shows the first 8 seconds, acceleration has decreased from 2.78 to 2.0 m/s$^2$. If we plot velocity over time, we see that speed decelerates to 110 m/s in 165 seconds, stall speed is never reached.

If we repeat the exercise for an initial speed of 160 m/s = 576 km/h = 311 kts, and at the same weight of 18,000 kg, we reach stall speed of 61.11 m/s after 66 seconds, if the pilot keeps the thrust at the same setting. They have plenty time to speed up. The plot also shows what we find if we use the initial acceleration only, a time of 36 seconds.

After reaching stall speed it will take a very short time before the aircraft comes to a stop: it falls out of the sky. A shallow dive cures that: gravity now produces a thrust component as well, with $T_G = m \cdot g \cdot sin(\Theta)$. At 18,000 kg, a dive angle of 16° is enough to maintain airspeed without adding thrust while firing the gun: the gravity component now exactly compensates for the thrust of the gun.

Sorry, I am a little confused about the table. I expect D is drag, which equals thrust (since the first value is about ~80kN), but what then is T? From the end point, it would appear T is thrust, since you imply the aircraft won't decelerate any further once D=T, but then T should be 80kN at the start. Also a little lost in the jump from eqn. 1,2,3 as to how to calculate a, and D (which is a function velocity)? Thanks in advance!

@Penguin have added an explanation on the table, plz let me know if it helps. A = aspect ratio, computer from $b^2/S$. Drag is computed analogous to (2): $D = C_D \frac{1}{2} \cdot \rho \cdot V^2 \cdot S$, it is a function of velocity squared.

Yes! That makes it crystal clear. Thanks very much.

"Starting at 120 m/s, a dive angle of 16° is enough to maintain airspeed" but only for a time shorter than your initial altitude in meters divided by 33, afterwards you will have a really close encounter with the ground.

As an A10A avionics tech, I would only add that the Stability Augmentation System adds 1.9° up deflection to the elevators while the trigger is depressed to counter the downward vector of the gun being fired. Most pilots are not aware of this, but it would tend to reduce the 'feel' of the gun recoil.

What acceleration is being applied to the aircraft (In m/s or kt/s)?

From XKCD we know that the gun

produces almost five tons of recoil force

that is about 50000 newtons (round numbers for simplicity, they won't overly affect the results)
The acceleration is force divided by mass, and the A-10 has an empty mass of 11000 kg, and a MTOW of 23000 kg.
This gives an acceleration between $4.545\ \mathrm{m/s^2}$ and $2.174\ \mathrm{m/s^2}$.
The Wikipedia page about the GAU-8 mentions that

While this recoil force is significant, in practice a cannon fire burst slows the aircraft only a few miles per hour in level flight.

and gives as a reference a book that I do not own, so I cannot verify.

If there was infinite ammo and nothing like gun overheat, how long would it take to slow the plane down to stall speed, if initial speed was a usual A-10 speed.

With the additional assumption of thrust balancing only the aerodynamic drag, we can say the following: cruise speed is $155.6\ \mathrm{m/s}$, and stall speed is $61.11\ \mathrm{m/s}$ (see Wikipedia link above), so this means that it would take between ~34 and ~71 seconds to completely stop the aircraft; or between ~20 and ~43 seconds to stall it.

If instead we want to be more realistic, we have to assume that we have infinite fuel, that ammo and fuel do not factor in the weight computation, and that the yawing/pitching moments do not overcome actuator authority.
With all that in mind, we should start from firing the gun at strafe speed, not at cruise speed, since we want to hit a specific target on the ground, so we want to move as slowly as possible, to have the highest chances of hitting it. This means that our starting velocity would be above stall speed but not significantly, leading to a smaller margin of continuous fire before stalling, unless the throttle is opened (if possible) to counteract the extra "drag".
If we ignore the discussion about strafing and hitting the target, and we fire from cruise speed (and this is what is meant by "usual speed"), it is possible that stall is not achieved, since at lower speeds you will have more excess thrust (but we are still assuming that the firing only produces "drag" or a negligible amount of yawing/pitching moments). This means that we could settle at a lower speed, but the determination of the exact speed requires the knowledge of the exact drag and thrust characteristics of the aircraft, in addition to it being a function of the initial speed, see Koyovis' answer for some basic numbers.

Comments are not for extended discussion; this conversation has been moved to chat. Additional comments will be deleted without being moved to chat.

I asked this question of an A-10 pilot at the Stewart, FL airshow. His response was that the recoil from the guns wasn't noticeable. However, the exhaust generated by the spent shell casings (smoke, particulate) tended to get into the engines and cause issues. Hence the relatively short bursts followed by periods of non-firing to let the engines clear.

A guy I work with flew earlier A-10s and said the recoil was overplayed. He never offered numbers, but clearly poo pooed the effect on flight. That supports the comments of your contact.

Specifically, the gases generated by the gun firing are oxygen poor, so if they get into the engine it can cause a flame out due to lack of oxygen. In order to counteract this, A-10 pilots are recommended to fire in 3-4 second burts and the pilot light for the engine is triggered to engage when the gun is firing.

A pilot isn't really a good authority on this.  I can drive up a hill in my car and while I may know I'm pressing a little harder on the accelerator, I have no frame of reference to estimate how much more fuel is being consumed to counteract the upward incline.

@DeanMacGregor I would disagree. A typical car driver isn't really a good comparison to a pilot. Pretty much every pilot has a much-better-than-average knowledge of their vehicle. An Indy car driver would be more applicable, and I'd bet an Indy driver could give you a pretty close estimate of gas consumption on that hill.

Note that the guns are fired in bursts only (per designer specs, pilot training, and pilot anecdotes). The thrust from a short burst may not act long enough to be noticeable by the pilot, but sustained firing for the durations discussed in other answers (30-120 seconds) would be. Still upvoting because this demonstrates the typical real-life usage of the gun; other answers already cover the theoretical effects.